Inner tube



Patented Nov. 17, 1936 UNITED STATES PATENT OFFICE INNER TUBE Walter E. Sh'vely, Fairlawn, Ohio, assignor to Wngfoot Corporation, Wilmington, Del., a corporation of Delaware Application February 17, 1934, Serial No. '711,739

13 Claims. (Cl. 154-14) This invention relates to inner tubes for Veagent polyglycerol or Turkey-red oil, etc. may be hicle tires. More particularly it relates to an p oye d. LateX in V y &11101111135 may be inner tube covered on the inside with a gas-imadded'to the gaS-mPeYVOUS film if d s The pervious coating which is protected by a water- Ceating y be pp d y dSSOIVng p resistant oang ing the colloid in water and adding the plasticzer 5 several t manufa ture s have been market and such other ingredients as are desirable and ing an m t coated With gasqmpervjous allowing the water to evaporate before vulcanizfi such as a fi of m and poygycerol ing. One coat or several coats of the coating ma- Tubes of this type have been found to lose less terial may be appliedair in service than ordinary tubes which are not A layer tWO to three thousandths Of an hch 10 So Goated' However, atings of this type have thick of gelatin, plasticized with polyglycerol or b found t have only a limited life The air other suitable plasticizer forms a preferred gasin inflated tubes is compressed and the humidity imperVOuS Boating- A Coathg composition made is high and changes in temperature cause conp 50 p rts by Weight of water, 16 /3 Parte by densation of water in the tubes. Water thus con- Weight 0f gelatih and /3 parts by Weig Of densed or otherwise admitted to the tubes dis- Polyglyeerol, if b d OYltO` th be in uc a solves out the polyglycerol or other plasticizer Way that there S about pound Of the tio used for the gelatin or t upon t gelatin in for each 1000 square inches of tube surface will be some way and the coating material separates. At found be quite p vio W dried. A

20 any rate it has been found that eventually in such Tubbel" nner tube lned With Sheh e Boating, P 20 tubes the gelatin hardens and becomes separated tected from moisture by an elastic adherent waterfrom the tube, after which the tubes are no more oo coating constitutes a p rr form of th gas-impervious than uncoated tubes. nVentOne According to this invention the gas-impervious The Water-%Sistem COVerng ust b elaSt C coating on the inner tub s i m d w t within the limits necessitated by the stretching 25 sistant. This has been found to give the coating Of the b i u a sh uld be of such a commuch longer life, and, in the preferred form of the position that it adheres te the D V OUS invention, as long alife as the tubes themselves. COathg eVen after being p a d y stretched Inner tubes for automobile tires as now manuand subjected to the tO oIS Wh ch nner factured are smaller in circumference and damtubes undergo in use. To be effective it must be 30 eter in the uninfiated state tha in the infiated water-resistant after such repeated stretching. state. In other Words, after the tube is inserted A ruhber COVeriIlg, pp d aS a ubb r cement in the tire and infiated it is stretched materially. has been found most satisfactory. The aw Usually the cross-section of the inflated tube in ShOWS a portion Of the a Of n i ner tube the tire is some 20 or 30 er cent greater than the o d W t a gas mpervous l y which s p o- 35 cross-section of a tube which is filled with air but tected by a fi A single o t of rubber not stretched, and the circumference of the tube cement containing about o rubber and in service is several per cent' greater than the tube Suffieent Sulfur three pe cent) &ndan filled with air, but not stretched. Because of this accelerator to vulcanze h u r Wh n dry v s 40 stretching of the tube d the continua fiexing a coverng which is water-resistant and adheres 40 to which the tube is subj ected in use it is necessary StrOnglY tO the D HS a g a ter rethat the gas-impervious coating and the waterpeated Stretchng d fiexing, a d even for the proof'coating shall be both elastic and also gas- 1e Of the u The ubb r may be dissolved impervous nd water-proof, re tiv i the in any suitable solvent. A mixture of benzene stretche-d condition. Furthermore, to be effective and rubber-solVent gSOlne s p oved most they must still adhere to the tube after being satisfactory. If y gaSOlne is used the coatstretched and then allowed to return to the uning has b found to o m bubbles and after stretched condition. They must also withstand vulcanizing the surface is not as smooth as when temperature changes to which tubes are subjected SOme benZene S mixed With A cement from in use, Smoked rubber will ordinarily be used. Cements 50 In the manufacture of tubes with a gas-immade from p p latex, Or Other forms of pervious coating as now carried out a jel-forming ubb may be u ed. hydrophyllc colloid and plasticizer have been em- The coatings are preferably applied to the played. Glue, casein, haemoglobin or other suitinner tubes by placing them on a mandrel of 5 'able colloid may be used and as a plasticizing proper diameter which may be either straight or curved. The gas-impervious coating is first applied by brushing, spraying or dipping and then after drying, the water-proofing layer is applied by brushing, spraying or dipping or in any other suitable way. After the application of each coat of material the tubes are permitted to stand for a sufi'icient period of time to allow substantially complete evaporation of the Volatile liquids contained within the coating materials before a subsequent coat is applied. Several coats of either or both coating materials may be used if desired. Coatings of the gelatincontaining composition may be alternated with coatings of the rubber cement. Each coat is preferably allowed to dry before the application of the next coat. After the various coatings have been applied and the tubes have been allowed to dry they are stripped from the mandrels and turned inside out so that the coating is on the interior surface of the tube. The ends of the tube are then joined to form an annulus, after which the coated tube is subjected to vulcanization in the usual molds in the ordinary manner.

If preferred, the tubes may be cured directly upon the mandrels and then be stripped off of and turned inside out. The ends of the cured tubes may then be buifed, cemented and spliced in the same manner as ordinary mandrel-cured tubes.

Tubes coated With gelatin and polyglycerol, with a covering of rubber applied as vulcanizable cement may be stretched and flexed even to the point of breaking or bursting without any tendency toward separation between the various coatings or the interior coating and the inner surface of the tube. In spite of repeated Stretching and flexing the continuity of the films is not broken. The impermeability of the composite film covering to inating media, such as air or other gas, and the resistance of the film to water, is unimpaired after prolonged use on an auto, truck, bus or other vehicle.

In addition to preventing the gas-impervious layer from becoming attacked by water the layer of rubber formed from the cement appears to protect it from chafing and wearing and thus prolong its life. Any suitable protecting coating may be used instead of rubber cement. It must be of such composition that it adheres to the gas-impervious coating under the conditions of use and withstands the temperature employed for vulcanizing or subsequent use of the tube in service.

What I claim is:

1. A rubber inner tube for vehicle tires, the interior surface of which is covered with a thin non-water-resistant coating which is more impervious to the passage of gas under pressure than rubber, and protecting this coating a closely adhering water-resistant rubber film.

2. A rubber inner tube for vehicle tires, the interior surface of which is coated with a thin gelatin-containing coating which is more impervious to the passage of gas under pressure than rubber, and protecting this coating a closely adhering water-resistant rubber film.

3. A rubber inner tube for vehicle tires, the interior surface of which is covered with a thin poly-glycerol-containing coating which i'smr impervious to the passage of gas under pressure than rubber, and covering this a closely adhering water-resistant rubber film.

4. A rubber inner tube for vehicle tires, the interior surface of which is covered with a thin non-fiuent coating of gelatin and a water-soluble plasticizer which coating is more impervious to the passage of gas under pressure than rubber, and protecting this coating a closely adhering water-resistant rubber film.

5. A rubber inner tube for vehicle tires the interior surface of which is covered with a thin, non-fluent layer of gelatin and poly-glycerol which is more impervious to the passage of gas under pressure than rubber, and protecting this coating a closely adhering water-resistant rubber film.

6. The steps in the manufacture of a rubber inner tube for vehicle tires which comprises applying a thin gas-impervious coating of watersoluble material to vulcanizable inner tube material and. thereafter protecting this coating by covering it with a film of rubber and then Vulcanizing.

'7. The method of manufacturing a rubber inner tube for vehicle tires which comprises covering vulcanizable inner tube material with a gas impervious coating of gelatin and poly-glycerol, covering this with a layer of vuicanizable rubber cement and then simultaneously vulcanizing the tube material and the cement.

8. A rubber inner tube for vehicle tires coated on the interior with a thin closely adhering waterresistant covering which is more impervious to the passage of gas under pressure than rubber.

9. A rubber inner tube for vehicle tires, the interior surface of which is covered with a thin non-water-resistant coating which is more impervious to the passage of gas under pressure than rubber, and protecting this coating a closely adhering water-resistant film.

10. A rubber inner tube for vehicle tires, the interior surface of which is coated with a thin gelatin-containing coating which is more impervious to the passage of gas under pressure than rubber, and protecting this coating a closely adhering water-resistant film.

11. A rubber inner tube for vehicle tires, the interior surface of which is covered with a thin poly-glycerol-containing coating which is more impervious to the passage of gas under pressure than rubber, and covering this a closely adhering water-resistant film.

12. A rubber inner tube for vehicle tires, the interior surface of which is covered with a thin non-fluent coating of gelatin and a water-soluble plasticizer' which coating is more impervious to the passage of gas under pressure than rubber, and protecting this coating a closely adhering water-resistant film.

13. A rubber inner tube for vehicle tires the interior surface of which is covered with a thin, non-fiuent layer of gelatin and poly-glycerol which is more impervious to the passage of gas under pressure than rubber, and protecting this coating a. closely adhering water-resistant film.

WALTER E. SI-IIVELY. 

